CVE-2020-15135

save-server (npm package) before version 1.05 is affected by a CSRF vulnerability, as there is no CSRF mitigation (Tokens etc.). The fix introduced in version version 1.05 unintentionally breaks uploading so version v1.0.7 is the fixed version. This is patched by implementing Double submit. The CSRF attack would require you to navigate to a malicious site while you have an active session with Save-Server (Session key stored in cookies). The malicious user would then be able to perform some actions, including uploading/deleting files and adding redirects. If you are logged in as root, this attack is significantly more severe. They can in addition create, delete and update users. If they updated the password of a user, that users files would then be available. If the root password is updated, all files would be visible if they logged in with the new password. Note that due to the same origin policy malicious actors cannot view the gallery or the response of any of the methods, nor be sure they succeeded. This issue has been patched in version 1.0.7.

Weakness

The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.

Affected Software

Potential Mitigations

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, use anti-CSRF packages such as the OWASP CSRFGuard. [REF-330]
• Another example is the ESAPI Session Management control, which includes a component for CSRF. [REF-45]
• Use the “double-submitted cookie” method as described by Felten and Zeller:
• When a user visits a site, the site should generate a pseudorandom value and set it as a cookie on the user’s machine. The site should require every form submission to include this value as a form value and also as a cookie value. When a POST request is sent to the site, the request should only be considered valid if the form value and the cookie value are the same.
• Because of the same-origin policy, an attacker cannot read or modify the value stored in the cookie. To successfully submit a form on behalf of the user, the attacker would have to correctly guess the pseudorandom value. If the pseudorandom value is cryptographically strong, this will be prohibitively difficult.
• This technique requires Javascript, so it may not work for browsers that have Javascript disabled. [REF-331]

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/111.html
• https://cwe.mitre.org/data/definitions/462.html
• https://cwe.mitre.org/data/definitions/467.html
• https://cwe.mitre.org/data/definitions/62.html

References

• https://github.com/Neztore/save-server/security/advisories/GHSA-wwrj-35w6-77ff
• https://medium.com/cross-site-request-forgery-csrf/double-submit-cookie-pattern-65bb71d80d9f
• https://www.npmjs.com/package/save-server